Our invention pertains to an electropneumatic door control system. More particularly, the invention pertains to an improved door control arrangement in which the door opening is enabled only when the train has stopped at a station and an open door condition locks the station or parking brake of the train separately from the regular braking.
Electropneumatic door controls with reverser apparatus are used primarily in public transportation facilities, for example, such as passenger buses. The controls are generally activated either pneumatically or electropneumatically when the driver actuates a control device to open or close the door in accordance with his desires. This action, by means of a door control valve, sends compressed air to a door drive mechanism designed as a door cylinder in which the stroke movements of the cylinder piston actuate the opening and closing motions of the door, which is generally of a type which has two portions which fold or move in opposite directions to provide the passenger opening. Since such doors have to be operated under all sorts of operating conditions, including improper operation by passengers, the control has to fulfill a number of limiting conditions. For example, it is generally required that the closing motion of a pneumatically-operated vehicle door automatically reverse into an opening motion if persons or objects are caught in the closing door The door must also operate under severe operating conditions which occur, for example, in the colder part of the year when the kinematics of the door change due to low temperature and when movement of the door can be blocked by snow or ice. There is also a danger that persons or objects can be caught in the door during an opening motion. Since the reversal of the direction of an opening door would present additional danger for subsequent persons entering or leaving the vehicle, it is customary to provide an electropneumatic switching device which brings the opening door to a stop by exhausting the pneumatic equipment.
It has become apparent that the large number of specific limiting conditions for the door operation cannot be satisfied with the traditional electromagnetic equipment except at a relatively high cost. To create such a door control system which is capable of meeting all the required conditions simply and at a low cost, that is, specifically without the use of additional valves or pressure switches, it has been proposed that an electronic system be provided to monitor and control the door. This electronic arrangement includes a door position flip-flop as an electronic indication of the existing door position. A basic system of this type is disclosed in the copending U.S patent application, Ser. No. 295,393, filed Aug. 24, 1981, Pat. No. 4,478,131, for Peter Liermann et al, entitled Electropneumatic Door Control Apparatus, which has a common assignee with the present application. However, it has been found desirable to add to the basic system disclosed in that application so that the doors may be opened only when the vehicle is assuredly stopped, that with the doors open a station or parking brake is separately applied, and that an audible warning is provided before the vehicle doors begin to close.
Accordingly, an object of our invention is an improved vehicle door control system employing electronic circuitry to control the electropneumatic elements and providing assurance that the vehicle has stopped prior to opening the doors and that it remains stopped while the doors are in the open condition.
Another object of the invention is a door control system for transit vehicles including electronic control arrangements, for the electropneumatic door controllers, which further enables the opening of the vehicle doors only when the vehicle is fully stopped, holds engaged or active the station or parking brake while the doors are open, and provides an audible warning signal for a timed period prior to the reclosing of the doors
Other objects, features, and advantages of this invention will become apparent from the following specification and appended claims when taken in connection with the accompanying drawings.